Functional Description - Silicon Laboratories EFR32xG14 Wireless Gecko Reference Manual

30.3 Functional Description

Software drivers provided by Silicon Labs offer a simple API interface to the TRNG module. It is highly recommended to use the provi-
ded software librariesto access the TRNG module. An overview of the TRNG module is shown in
1012.
TESTDATA
Entropy Source
30.3.1 Built-In Tests
The TRNG module includes several built-in tests to detect issues with the noise source, ensure entropy, and meet cryptography stand-
ards.The Repetition Count Test and Adaptive Proportion Test with window sizes of 64 and 4096 bits described in section 6.5.1.2 of
NIST-800-90B (http://csrc.nist.gov/publications/drafts/800-90/draft-sp800-90b.pdf) are implemented in hardware and run continuously
on the data. All three tests have corresponding interrupt flags that can optionally be used to generate a system interrupt.
The AIS31 Online Test described in section 5.5.3 of
tionen/AIS_31_Functionality_classes_for_random_number_generators_e.pdf
on the data. Both the preliminary noise alarm and the noise alarm are optionally available as interrupt sources from the TRNG module.
If a noise alarm occurs, the TRNG will be shut down, and must be reset with a software reset.
Additionally, the NIST-800-90B and AIS31 startup tests may be optionally enabled or disabled by software. The NIST-800-90B startup
test is enabled if the CONTROL_BYPNIST bit is cleared to 0. The AIS31 startup test is likewise enabled when CONTROL_BYPAIS31 is
cleared to 0. If either the NIST-800-90B or AIS31 startup tests are enabled, no data will be written to the output FIFO until the startup
requirements for these tests pass.
30.3.2 FIFO Interface
The TRNG module includes a 64-word output FIFO to hold the output data as it becomes available. The number of 32-bit words availa-
ble in the FIFO may be checked at any time by reading the FIFOLEVEL register. When the FIFO is completely filled, the TRNG will be
shut down, the STATUS_FULLIF flag will be set, and no further data will be written to the FIFO until the FIFO has been flushed. Data
may be read from the FIFO one word (32-bits) at a time via the FIFO register. The STATUS_FULLIF flag is cleared upon reading the
FIFOLEVEL register.
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TRNG Module
128-bit
KEY
TESTEN
Startup and
Online Tests
Interrupts and
Alarms
Figure 30.1. TRNG Overview
https://www.bsi.bund.de/SharedDocs/Downloads/DE/BSI/Zertifizierung/Interpreta-
TRNG - True Random Number Generator
Figure 30.1 TRNG Overview on page
CONDBYPASS
Conditioning
Function
is also implemented in hardware, and runs continuously
Reference Manual
64 x 32-bit
FIFO
Rev. 1.1 | 1012